The present invention relates to novel polyelectrolytes and mixtures thereof with cationic polymers and, more particularly, this invention relates to polyquaternary terpolymers and membranes of films prepared from mixtures of the terpolymer with various cationic homopolymeric polyelectrolytes.
Electrode surfaces have been modified by grafting cationic compounds, such as the bipyridinum compound, methyl viologen, or by adhering a coating of polyelectrolyte to the surface to provide the surface with high affinity for counter ion reactants. These reactants can be incorporated into the polyelectrolyte layer by ion-exchange. This tactic was first demonstrated with poly-4-vinyl pyridine (Oyama, N., Anson, F. C., J. Electrochem. Soc., 1980, 127, 247). Numerous polyelectrolytes have since been tried as electrode coatings (Majda, M., Faulkner, L. R., J. Electroanal. Chem., 1984, 169, 77 and the references cited therein).
Previously available polyelectrolyte systems useful for coating electrodes lack one or more of the essential properties required for effective electrode coatings. These include strong, irreversible binding of the polyelectrolyte to electrode surfaces, reasonable ion-exchange capacities of the coatings, retention of counter-ionic reactants by the coatings for long periods in solution containing none of the counter-ions, rapid charge propagation rates within the coatings and reasonable chemical and mechanical stability. Most commonly available ionic polymers are either too soluble in water or support facile counter-ion exchange so that incorporated ionic reactants are rapidly lost from the polyelectrolyte electrode coating.
Of the polyelectrolytes that have been applied to electrode surfaces in order to bind electroactive counter-ions, the one which has exhibited the most of these desired properties is a block copolymer based on poly (1-lysine), PLC (Anson, F. C., Saveant, J. M., Shigehara, K. J., Am. Chem. Soc., 1983, 105, 1096). For example, PLC provides much higher charge propagation rates than are available with otherwise attractive coatings prepared from Nafion (a fluorinated, sulfonated polymer). Coatings of protonated or quaternized poly (4-vinylpyridine), PVP or QPVP, are less adherent than PLC and much inferior in retaining incorporated anions when transferred to pure supporting electrolyte solutions. The latter shortcoming is also shared by non-cross-linked polystyrene sulfonate.